No.  1091 


INSTRUCTIONS 

FOR 

PROOF  OF 
GUNS  md  CARRIAGES 

INCLUDING  STAR-GAUGING  OF  GUNS 
and  TAKING  IMPRESSIONS  OF  BORE 


{ONE  PLATE) 


FEBRUARY  16,  1905 
REVISED  NOVEMBER  7,  1906 
REVISED  MARCH  11,  1908 
REVISED  JANUARY  28,  1913 
REVISED  JUNE  7,  1916 


WASHINGTON 

GOVERNMENT  PRINTING  OFFICE 
1916 


I 


(Form  No.  1091.) 

THE  OFFICIAL  NUMBER  OF  THIS  COPY 


■s  213 


The  Commanding  Officer  or  the  Post  or  Coast  Defense 
Ordnance  Officer  to  whom  this  copy  is  issued  will  be 
held  personally  responsible  for  its  safe=keeping.  When 
another  officer  relieves  him  a receipt  for  it  by  number 
will  be  taken,  which  should  be  mailed  to  the  CHIEF  OF 
ORDNANCE,  U.  S.  Army,  Washington,  D.  C. 

B ■ ■■■■-.  


NOTE. — This  pamphlet  may  be  destroyed  when  super- 
seded by  one  of  later  date. 


(2) 


U/VA?)  P 


War  Department, 

Office  of  the  Chief  of  Ordnance, 

Washington,  June  7,  1916. 

This  manual  is  published  for  the  information  and  government  of  the  Regular  Army 
and  Organized  Militia  of  the  United  States. 

By  order  of  the  Secretary  of  War: 

William  Crozier, 

Brigadier  General,  Chief  of  Ordnance. 


46153— IG 


(3) 


Digitized  by  the  Internet  Archive 
in  2016  with  funding  from’' 

University  of  Illinois  Urbana-Champaign  Alternates 


https://archive.org/details/instructionsforp00unit_1 


GENERAL  INSTRUCTIONS. 


1.  Before  proof-firing,  both  gun  and  carriage  should  be  carefully 
inspected,  inspection  blanks  used  by  armament  officers  for  semiannual 
inspections  being  taken  as  guides.  Care  should  be  taken  that  both 
are  in  perfect  working  order.  Similar  inspections  should  be  made 
after  the  proof-firing,  and  reports  made  out  giving  all  the  informa- 
tion on  the  blanks  referred  to  above,  including  items  under  firing; 
any  breakage  or  irregular  action  of  gun  or  carriage  being  carefully 
noted. 

2.  The  proof-firing  at  fortifications  will  always  be  under  the  charge 
of  the  armament  officer,  except  in  special  cases  where  authority  to 
omit  this  requirement  is  obtained  from  the  Chief  of  Ordnance. 

3.  The  ammunition  to  be  used  in  the  proof -firing  should  be  exam- 
ined by  the  proof  officer  to  see  that  it  is  standard  in  all  particulars; 
he  should  especially  note  the  powder  used  to  make  certain  that  it  is  for 
the  caliber  and  model  of  gun  in  which  it  is  to  be  fired. 

4.  In  all  cases  where  new  guns  are  fired,  for  whatever  purpose, 
the  gun  will  be  star-gauged  before  firing,  and  again  after  comple- 
tion of  the  number  of  rounds  prescribed  for  the  proof  of  each  gun,  for 
the  purpose  of  funiishing  the  data  required  for  the  inspection  report. 

5.  Before  star-gauging  the  gun  the  bore  and  chamber  must  be 
thorougldy  cleaned  in  order  that  all  residue  or  dirt  may  be  removed 
therefrom.  For  this  purpose  special  wire  cleaning  brushes  have  been 
issued  to  each  district  armament  officer.  Special  cleaning  tools  for 
removing  copper  deposit  and  residue  in  extreme  cases  have  been 
designed.  If  required,  and  not  on  hand  in  the  armament  district, 
application  should  be  made  to  the  Chief  of  Ordnance.  Lavaline  is 
also  issued  for  use  in  cleaning  the  bore  of  guns.  ^Vfter  proof-firing, 
special  attention  will  be  given  to  the  development  of  cracks  in  the  tube, 
particularly  near  the  muzzle  end.  Every  defect  discovered  will  be 
recorded,  with  such  measurements  or  impressions  taken  as  wiU 
enable  any  increase  in  its  amount  to  be  determined. 

6.  While  the  Ordnance  Office  will  endeavor  in  some  cases  to  pro- 
vide powder  in  advance  of  ordering  material  proof-fired,  this  should 
not  be  depended  upon;  the  officer  in  charge  of  making  these  proof- 
firings  should  assure  himself  that  the  post  is  supplied  with  the  neces- 
sary powder,  and  if  it  is  not  he  should^  make  requisition  therefor. 


6 


7.  Whenever  a district  armament  officer  is  cognizant  of  the  fact 
that  armament  in  his  district  will  soon  be  ready  for  proof-firing  he 
should  submit,  in  advance,  a special  requisition  for  the  necessary 
powder  charges. 

8.  Powder  charges  for  proof-firing  will  be  accompanied  by  a print 
of  the  charge-pressure  curve  of  the  powder  in  question,  and  the  proof 
officer  should  have  this  in  his  possession  or  assure  himself  that  it  is  at 
the  post  before  proceeding  thereto  for  proof-firing.  The  charges 
should  be  fired  as  issued  unless  it  is  apparent  that  the  powder  is  giving 
consistently  higher  pressures  than  anticipated,  in  which  case  the 
larger  charges  should  be  reduced,  using  the  charge-pressure  curve  as  a 
guide.  Unless  the  powder  is  giving  pressures  more  than  5 per  cent 
above  those  anticipated,  it  should  not  be  necessary  to  reduce  any 
but  the  15  per  cent  excess  pressure  charge. 

INSTRUCTION  FOR  PROOF-FIRING  OF  GUN  CARRIAGES. 

1.  Contracts  for  all  carriages  require  that  prior  to  acceptance  they 
shall  withstand  the  firing  of  a certain  number  of  rounds  at  such 
place  as  the  department  may  prescribe;  this  provision  is  sometimes 
waived  to  avoid  too  long  withholding  the  final  payment  for  the  car- 
riage. In  the  case  of  seacoast  carriages  and  in  the  absence  of  instruc- 
tions to  the  contrary,  when  a carriage  is  mounted  in  a fortification 
without  having  been  previously  proof-fired,  the  requirements  as  to 
proof  thereof  are  considered  as  fulfilled  by  the  following,  viz : 

2.  Each  gun  and  carriage  after  being  mounted  in  a fortification 
shall  be  fired  four  rounds  with  charges  giving  pressures  as  follows : 

(a)  Seventy-five  per  cent  of  maximum  service  pressure  to  be  fired 
at  such  elevation  as  local  conditions  or  data  to  be  obtained  make 
desirable. 

(b)  Maximum  service  pressure  to  be  fired  at  such  elevation  as  local 
conditions  or  data  to  be  obtained  make  desirable. 

(c)  One  hundred  and  ten  per  cent  of  maximum  service  pressure  to 
be  fired  at  the  minimum  elevation  permitted  by  the  carriage.^ 

id)  One  hundred  and  fifteen  per  cent  of  maximum  service  pressure 
to  be  fired  at  the  maximum  elevation  permitted  by  the  carriage.^ 

Each  gun  and  carriage  after  having  been  disassembled  and  re- 
mounted in  a fortification  shall  be  fired  two  rounds  with  charges 
giving  pressures  as  follows: 

(a)  Seventy -five  per  cent  of  maximum  service  pressure  to  be  fired 
at  the  minimum  elevation  permitted  by  the  carriage.^ 

(b)  Maximum  service  pressure  to  be  fired  at  the  maximum  eleva- 
tion permitted  by  the  carriage.^ 

1 When  local  conditions  do  not  permit  firings  at  extremes  of  elevation  with  safety,  elevations  as  near 
these  limits  as  possible  consistent  with  safety  will  be  used. 


7 


The  maximum  service  pressures  referred  to  above  are  those  given 
under  the  heading  ^‘Maximum  pressure’’  of  the  table  under  Ballistic 
Test — Ordnance  Department  Pamphlet  450,  Specifications  for  Cannon 
Powder,  except  in  proof-firing  carriages  for  guns  enumerated  in  table 
below  the  standard  pressure  will  be  that  indicated  opposite  the  re- 


spective guns. 

3-inch  (15-pounder)  gun,  model  of  1903 40,000 

5- inch  guns,  model  of  1900 38, 000 

6- inch  guns,  models  of  1900,  1903,  and  1905  39, 000 

10-inch  guns,  model  of  1900 38,  000 

12-inch  guns,  model  of  1900 39, 000 


All  14-inch  gun  carriages,  in  addition  to  the  prescribed  proof  rounds 
mentioned  under  a,  h,  c,  and  d of  paragraph  2 above,  will  be  fired  an 
additional  round  with  pressure  approximately  47,000  pounds  per 
square  inch. 

In  the  absence  of  special  instructions  from  the  department,  the 
proof  of  armament  mounted  in  fortifications  will  be  made  as  pre- 
scribed in  this  paragraph,  excepting  that  the  district  armament 
officer  may  in  special  cases  be  authorized  to  fire  such  additional 
rounds  as  may  be  necessary  in  view  of  the  results  of  the  regular  proof 
rounds. 

3.  Where  the  gun  mounted  thereon  lias  not  previously  been  proof 
fired,  all  necessary  data  in  regard  to  the  operation  of  the  carriage 
will  be  obtained  from  the  firings  required  for  the  proof  of  the  gun. 

4.  Prior  to  making  the  firings  the  following  action  should  bo  taken 
as  far  as  applicable  in  each  case,  viz: 

(a)  Adjust  elevating  friction  device  as  prescribed  in  the  handbook 
for  the  carriage. 

(b)  Make  similar  adjustment  for  the  traversing  friction  device. 

(c)  Set  throttling  valve  at  zero,  and  see  that  it  is  properly  assem- 
bled. 

(d)  See  that  recoil  cylinders  arc  properly  filled. 

(e)  See  that  all  working  parts  of  carriage  are  clean  and  well  lubri- 
cated. 

5.  If  the  carriage  has  not  previously  been  proof  fired,  the  record  of 
proof  firing  will  bo  entered  in  both  copies  of  shop  inspection  report 
if  available.  If  but  one  copy  is  available,  a duplicate  of  the  record 
of  proof  firing  with  all  remarks  as  to  breakages,  etc.,  will  be  made 
out  on  Form  No.  1116  and  forwarded  to  the  Chief  of  Ordnance  for 
insertion  in  the  original  copy  of  the  shop  inspection  report. 


8 


Inspection  and  proof  reports — carriages. 


Form 

No. 


Designation  of  blank  or  description  of  work. 


1069 

1070 

1071 

1072 

1084 

1085 

1086 

1114 

1115 

1116 

1117 

1118 
1120 
1122 

1123 

1124 
1134 
1141 
1144 
1150 
1152 
1154 
1161 
1166 
1167 


Report  of  inspection  of  barbette  carriages.  (2  sheets.) 

Report  of  inspection  of  rapid-fire  barbette  carriages.  (2  sheets.) 

Report  of  inspection  of  disappearing  carriages.  (5  sheets.) 

Report  of  inspection  of  mortar  carriages.  (2  sheets.) 

Inspection  report  of  6-inch  diappearing  carriages,  Iv.  F.,  model  of  1903,  No.  — . 

Inspection  and  proof  report  of  3-inch  gun  carriage.  No.  — , model  of  1902. 

Inspection  and  proof  report  of  5-inch  barbette  carriage,  model  of  1903. 

Inspection  report  of  12-inch  mortar  carriage,  model  of  1896,  Mii. 

Inspection  and  proof  report  of  15-pounder  barbette  carriage,  model  of  1903,  No.  — . 

Report  of  inspection, gun  and  carriage,  special  sheet  for  firings. 

Recommendations  and  remarks. 

Inspection  report  of  12-inch  disappearing  carriage,  L.  F.,  model  of  1901,  No.  — . 

Inspection  and  proof  report  of  4.7-inch  gun  carriage.  No.  — , model  of  1906. 

Inspection  report  of  6-inch  disappearing  carriage,  L.  F.,  model  of  1905,  Mi,  No.  — . 

Inspection  report  of  12-inch  mortar  carriage,  model  of  1908. 

Inspection  and  proof  report  of  3.8-inch  field  howitzer  carriage,  model  of  1908. 

Inspection  and  proof  report  of  6-inch  howitzer  carriage,  No.  — , model  of  1908. 

Inspection  and  proof  report  of  14-inch  disappearing  carriage,  L.  F.,  model  of  1907,  No.  — . 
Inspection  and  proof  report  of  4.7-inch  howitzer  carriage.  No.  — , model  of  1908. 

Inspection  and  proof  report  of  6-inch  disappearing  carriage,  L.  F.,  model  of  1905,  Mii,  No.  — . 
Inspection  and  proof  report  of  3.8-inch  gun  carriage.  No.  — , model  of  1904. 

Inspection  and  proof  report  of  6-inch  barbette  carriage.  No.  — , model  of  1910. 

Inspection  and  proof  report  of  12-inch  mortar  carriage,  model  of  1896,  Mm,  No.  — . 

Inspection  and  proof  report  of  3-inch  mountain  howitzer  carriage,  model  of  1911. 

Inspection  and  proof  report  of  4.7-inch  howitzer  carriage,  model  of  1908,  Mi. 


INSTRUCTIONS  FOR  PROOF  FIRING  GUNS. 

All  guns,  except  type  guns,  should  be  proof  fired  the  following 
number  of  rounds  before  acceptance,  unless  otherwise  specified  in 
the  contract: 

1.  All  1-pounder  guns  and  1-pounder  subcaliber  guns,  10  rounds; 
6 rounds  with  maximum  service  pressures,  2 rounds  with  10  per  cent 
above  maximum  service  pressure,  and  2 rounds  with  15  per  cent  above 
maximum  service  pressure. 

2.  All  guns  of  a caliber  greater  than  1 -pounder  and  less  than  8 
inches,  five  rounds — one  round  with  half  maximum  service  pressure, 
one  round  with  three-quarters  maximum  service  pressure,  one  round 
with  maximum  service  pressure,  one  round  with  10  per  cent  above 
maximum  service  pressure,  and  one  round  with  15  per  cent  above 
maximum  service  pressure. 

3.  Guns  of  8-inch  caliber  and  larger,  four  rounds — one  round  with 
three-quarters  maximum  service  pressure,  one  round  with  maximum 
service  pressure,  one  round  with  10  per  cent  above  maximum  service 
pressure,  and  one  round  with  15  per  cent  above  maximum  service 
pressure,  except  14-inch  guns  will  be  fired  an  additional  round  with 
pressure  of  approximately  47,000  pounds  per  square  inch. 

4.  The  maximum  service  pressures  referred  to  above  are  those  given 
under  the  heading  ^‘maximum  pressure”  of  the  table  under  Ballistic 
Test — Ordnance  Department  Pamplilet  450,  Specifications  for  Cannon 
Powder,  except  in  proof  firing  guns  noted  below  the  standard  pressure 
will  be  as  follows: 


9 


3-inch  (15-pounder)  gun,  model  of  1903 40,000 

5- inch  guns,  model  of  1900 38, 000 

6- inch  guns,  models  of  1900,  1903,  and  1905  39, 000 

10-inch  guns,  model  of  1900 38, 000 

12-inch  guns,  model  of  1900 39,000 


5.  Pressures  should  always  be  taken  when  proving  guns,  and  each 
part  of  the  gun  or  breech  mechanism  which  is  not  in  satisfactory  work- 
ing condition  should  be  reported  upon.  Whenever  practicable  the’ 
instrumental  velocity  of  each  round  will  be  taken. 

6.  The  gun  should  be  star-gauged  both  before  and  after  being  proof 
fired.  The  same  operator  should,  when  possible,  do  the  star-gauging 
for  the  same  gun  before  and  after,  as  it  will  insure  the  same  touch  on 
the  micrometer  handle. 

Inspection  and  proof  reports,  etc.,  guns. 


Form 

No. 


Designation  of  blank  or  description  of  work. 


1096 

2356 

1077 

1078 

1079 


Report  of  inspection  and  proof  of  — inch  — , No.  — , model  of  — . 

Extra  sheet  for  Form  No.  1096  for  additional  star-gauging  records. 

Record  of  measurements  of  — inch  — , No.  — , model  of  — (shrinkage  operations). 
Extra  sheet  for  Form  No.  1077. 

Do. 


STAR-GAUGING  GUNS. 

Two  sizes  of  star-gauges  are  in  use  in  the  service,  one  for  measuring 
cannon  up  to  and  including  3 inches  in  caliber,  and  a larger  one  for 
measuring  cannon  of  3-inch  caliber  and  larger.  The  larger  star-gauge 
has  two  heads,  one  for  measuring  cannon  of  S-inch  caliber  and  larger 
and  one  for  measuring  cannon  of  less  caliber. 

The  method  of  operating  the  two  star-gauges  is  the  same,  except 
that  with  the  smaller  star-gauge  bore  rests  are  unnecessary  and  are 
not  supplied. 

The  star-gauge  may  be  used  as  either  a two  or  three  point  gauge  by 
adjusting  the  head.  When  used  as  a two-point  gauge  four  identical 
points  are  inserted  in  the  head,  a paper  washer  about  0.004  inch  tliick 
being  inserted  under  the  two  opposite  ones  used  for  measuring.  The 
other  two  points  act  as  guides  and  tend  to  keep  the  head  centered  in 
the  bore.  Except  in  special  cases,  the  gauge  is  used  with  but  two 
points,  when  the  following  instructions  apply: 

To  star-gauge  a 12-inch  gun,  model  of  1895,  for  instance,  the 
method  employed  is  as  follows:  The  large  star  gauge  is  in  sections, 
each  50  inches  in  length.  To  the  head  section,  which  carries  the 
points,  the  additional  sections  are  added  until  the  gauge  is  of  suffi- 
cient length  for  the  gun.  The  micrometer  handle  is  then  screwed 
on,  the  scale  on  which  should  be  in  fine  with  the  figures  on  the  gauge. 


The  entire  gauge  should  be  assembled  in  front  of  the  breech  end  of 
the  gun  on  the  horses,  the  slides  on  which  have  been  adjusted  to  the 
proper  height. 

Insert  into  the  sockets  in  the  head  four  12-inch  points,  placing  the 
paper  washers  under  the  two  opposite  points  that  are  to  be  used  for 
measuring.  Take  the  ring  marked  “ 12-inch, which  is  supplied 
with  the  gauge,  and  have  it  held  by  the  assistant  so  that  when  the 
handle  is  turned  forward  the  two  measuring  points  will  touch  the 
inside  of  the  ring,  the  latter  being  kept  central  by  the  other  two 
points.  With  the  gauge  in  this  position  adjust  the  handle  so  that  it 
now  reads  zero.  The  muzzle  rest  is  then  adjusted  on  the  breech  so 
that  its  center  is  in  the  axis  of  the  bore.  The  three  arms  of  this  rest 
are  graduated,  and  the  rest  is  properly  located  when  the  readings  on 
all  arms  are  the  same.  The  gauge  is  now  inserted  in  the  bore  and 
moved  slowly  forward,  the  points  following  the  grooves,  until  it  is  at 
the  extreme  muzzle  end  of  the  gun.  The  gauge  should  be  moved 
muzzleward  until  the  head  and  points  clear  the  bore,  the  measuring 
points  turned  horizontal  and  the  head  reinserted  in  the  bore. 

The  grooves  and  lands  measured  should  be  indicated  by  prick-point 
marks  on  the  muzzle  face,  to  insure  the  measuring  of  the  same  grooves 
and  lands  before  and  after  proof  firing. 

The  operator,  standing  at  the  handle,  turns  it  so  that  the  two 
measuring  points  touch  the  bottom  of  the  grooves,  and  the  assistant, 
who  is  standing  in  rear  of  the  rest,  notes  the  number  of  inches  from 
the  breech.  The  scale  of  inches  is  on  the  gauge,  and  is  adjusted  so 
that  the  reading  is  taken  flush  with  the  rear  face  of  the  rest.  The 
assistant  calls  off  the  distance  and  the  operator  the  reading,  which 
is  in  thousandths  of  an  inch,  plus  or  minus,  depending  upon  whether 
the  reading  is  greater  or  less  than  the  ring  by  which  the  gauge  was 
adjusted.  The  recorder  enters  these  data  in  the  book.  The  operator 
then  turns  the  handle  slightly,  to  take  the  pressure  off  the  points 
and  the  assistant  withdraws  the  rod  5 inches  and  calls  off  this  dis- 
tance. The  operator  reads  the  measurement  and  calls  it  off,  the 
recorder  entering  both  in  the  book  as  before. 

This  is  repeated  every  5 inches  along  the  bore,  until  near  the  breech 
end,  where  it  enlarges.  From  this  point  on  the  readings  are  taken 
every  2 inches.  In  the  smaller  caliber  guns  the  readings  along  the 
entire  length  of  the  bore  are  taken  every  2 inches. 

When  inserting  the  gauge,  after  the  70-inch  mark  on  the  gauge  has 
passed  the  breech,  a bore  rest  is  placed  on  the  gauge  just  inside  the 
muzzle  rest.  These  rests  are  supplied  with  the  gauge  for  each  of 
the  different  calibers.  They  are  placed  every  70  inches,  although 
near  the  handle  this  distance  between  the  bore  rests  may  be  increased. 

If  it  is  impracticable  to  measure  the  bore  from  the  breech  end, 
it  may  be  measured  from  the  muzzle,  in  which  case  the  operation 


11 


is  the  same,  except  that  the  measurements  are  taken  as  the  gauge 
enters  the  muzzle  instead  of  as  it  is  withdrawn.  Plate  No.  1 shows 
the  bore  of  a 10-inch  gun  being  star-gauged  from  the  muzzle  end. 
In  this  case  it  was  impracticable,  on  account  of  obstructions,  to  meas- 
ure from  the  breech  end. 

After  completing  this  first  measurement  of  the  bore  the  gauge  is 
turned  90°,  so  that  the  measuring  points  are  vertical,  and  the  opera- 
tion is  repeated.  This  gives  a vertical  and  a horizontal  measure- 
ment of  the  grooves. 

The  lands  are  then  measured  in  the  same  manner,  both  a vertical 
and  a horizontal  measurement  being  taken.  In  measuring  the  lands, 
however,  the  proper  guide  plates  must  be  attached  to  the  end  of  the 
star-gauge  head.  The  guide  plate  is  secured  to  the  head  by  four 
screws.  The  guides  have  grooves  which  fit  over  the  lands,  being 
forced  outward  by  springs  against  the  walls  of  the  gun,  and  serve 
to  keep  the  points  on  the  lands.  There  is  a guide  plate  for  each  caliber 
gun.  Care  should  be  taken  to  see  that  the  guides  have  the  same 
pitch  as  the  rifling  of  the  gun. 

After  measuring  the  bore,  the  chamber  is  star-gauged.  Remove 
all  unnecessary  sections  from  the  gauge,  as  it  will  be  easier  to  handle. 
Put  on  14.2-inch  points  (in  case  of  12-inch  gun),  and  again  adjust 
the  handle  so  that  it  will  read  zero  when  the  ]u)ints  are  in  the  14.2- 
inch  ring.  The  measurements  of  the  chamber  should  be  taken  every 
2 inches,  with  the  measuring  points  horizontal,  and  the  same  repeated 
with  the  measuring  points  vertical.  The  advantage  of  measuring 
the  bore  from  the  bree(‘h  end  is  that,  after  measuring  the  bore,  the 
chamber  can  be  measured  without  changing  the  ])osition  of  the 
horses  or  of  the  muzzle  rest,  which  is  attached  to  the  breech  of  the 
gun,  thereby  effecting  a considerable  saving  in  time. 

In  star-gauging  the  chamber  of  guns  in  which  the  diameter  of 
the  powder  chamber  is  contracted  at  the  breech  end,  two  or  more 
special  hinged  points  must  be  used.  After  the  gauge  has  been 
adjusted  by  means  of  the  pro])er  ring,  the  hinged  points  are  turned 
down  to  allow  the  gauge  to  enter  the  chamber,  after  which  they  are 
turned  up  and  the  star-gauging  continued  as  in  the  ordinary  case. 

When  used  as  a three-point  gauge  aU  points  bear,  and  when  meas- 
uring the  lands  all  are  supplied  with  guides.  The  same  care  must 
be  observed  in  adjusting  the  guides  as  when  two  measuring  points 
are  used. 

Plate  No.  1 shows  the  muzzle  rest,  the  head  section,  and  the  points. 

Before  star-gauging  a gun,  the  bore  and  chamber  should  be  thor- 
oughly cleaned,  and,  if  necessary,  aU  copper  deposits  removed  with  a 
solution  of  sal  ammoniac. 

The  star-gauge  is  a delicate  instrument  and  should  be  handled 
with  the  greatest  care.  All  parts  should  be  kept  absolutely  free  from 
rust  and  the  working  parts  should  be  oiled. 


12 


Star-gauge  measurements  pertaining  to  the  manufacture  or  proof 
of  a gun  are  entered  on  Form  No.  1096,  and  those  relating  to  subse- 
quent firings  on  Form  No.  2356,  which  is  practically  a duplicate  of 
the  last  sheet  of  Form  No.  1096,  to  be  attached  thereto  to  complete 
the  record  of  the  gun. 

The  practice  at  Sandy  Hook  Proving  Ground  is  as  follows: 

The  rough  record  taken  at  the  time  of  the  star-gauging  is  entered 
in  a small  book  furnished  for  this  purpose  by  the  department.  This 
record  is  then  entered  in  a large  book,  also  furnished  by  the  depart- 
ment, the  measurements  recorded  being  the  mean  of  the  vertical  and 
horizontal  measurements  as  recorded  in  the  small  book.  The  entries 
on  the  blanks  referred  to  above  are  made  from  the  large  book,  which 
is  kept  as  a retained  copy  and  permanent  record. 

All  the  star-gauge  records  should  give  the  distance  from  the  face 
of  the  breech  of  the  gun  to  the  point  measured,  whether  the  original 
measurements  have  been  taken  from  the  breech  end  or  from  the 
muzzle  end  of  the  gun. 

When  a star-gauge  is  adjusted  to  a standard  ring  by  an  operator 
other  than  an  officer,  and  before  measurements  are  taken,  the  officer  in 
charge  of  the  work  will,  whenever  practicable,  personally  verify  the 
setting  of  the  micrometer  handle  and  the  use  of  the  proper  standard 
ring. 

The  record  book  will  show  for  each  star-gauging  of  a gun: 

The  name  of  the  operator,  the  name  of  the  officer  verifying  the 
adjustments,  the  temperature  of  the  air  inside  and  outside  of  the  bore, 
the  diameter  of  the  standard  ring  used  for  each  adjustment,  the  date 
and  number  of  rounds  fired  from  the  gun. 

A page  of  the  small  record  book  and  a copy  of  a portion  of  one  of 
the  completed  star-gauge  records  are  attached  hereto. 

Measurement  of  6-inch  gun,  W.  A.,  No.  4,  Model  of  1897  Mi. 


[a  page  op  small  record  book.] 
BEFORE  FIRING. 


Inches  from  breech. 

Lands. 

Grooves. 

Vertical. 

Horizontal. 

Vertical. 

Horizontal. 

27 7f  

6. 0010 
6.0030 
6. 0030 
6.0030 
6. 0030 
6.0020 
6. 0020 

6.0020 
6. 0020 
6.0010 
6.0010 
6. 0010 
6 
6 

6.0800 

6.0810 

6.0810 

6.0810 

6.0810 

6.0810 

6.0810 

6. 0800 
6.0810 
6.0810 
6.0810 
6. 0810 
6. 0810 
6.0810 

277  

275 

270 

265 

260  

255  

Measurement  of  6-inch  gun,  W.  A.,  No.  4,  Model  of  1897  Mi — Continued. 
[a  portion  of  one  of  the  completed  records.] 


Inches  from  breech. 

Lands. 

Grooves. 

Before 
firing, 
June  28, 
1902. 

After  24 
rounds, 
Oct.  10, 
1902. 

Difference. 

Before 
firing, 
June  28, 
1902. 

After  24 
rounds, 
Oct.  10, 
1902. 

Difference. 

277.75 

6.0015 
6. 0025 
6.0020 
6.0020 
6.0020 
6.0010 
6.0010 

6.0015 
6. 0020 
6. 0020 
6.0010 
6.0010 
6.0015 
6.0015 

6.0800 
6.0810 
6.0810 
6.0810 
6. 0810 
6.0810 
6.0810 

6. 0810 
6.0815 
6. 0815 
6.0810 
6. 0810 
6. 0815 
6. 0815 

+0. 0010 
+ .0005 
+ .0005 

277 

275 

-0.0005 

270 

- .66i6 

- .0010 
+ .0005 
+ . 0005 

265 

260 

255 

+ .0005 
+ . 0005 

DIRECTIONS  FOR  TAKING  GUN  IMPRESSIONS. 

Where  a more  minute  examination  of  the  l)oro  of  a gun  is  required 
than  can  be  obtained  hy  simple  inspection  with  the  use  of  lights  and 
a mirror,  or  whore  the  part  of  the  lioro  to  bo  examined  is  inaccessible 
to  those  means,  an  impression  of  the  bore  will  be  taken  on  gutta- 
percha. 

The  following  tools  are  required: 

One  smooth  board,  about  15  by  26  inches,  on  which  the  gutta- 
percha  is  rolled. 

One  roller  of  hardwood,  for  rolling  the  gutta-percha. 

One  iron  rod  J inch  in  diameter  and  from  15  to  20  feet  long.  About 
27  inches  of  this  rod  on  one  end  should  be  threaded. 

Two  nuts  and  washers  to  fit  the  aliove  rod. 

One  bar  of  iron  2 by  2 by  26  inches  with  a hole  in  the  center 
inch  in  diameter.  The  iron  rod  above  passes  through  this  hole  and 
a set  screw  in  the  bar  holds  it  in  place. 

One  pole  about  15  feet  long  with  ferrule  on  one  end  to  prevent 
its  splitting. 

One  kettle  for  heating  water. 

A sufficient  quantity  of  Dixon’s  No.  634  graphite. 

In  addition  to  the  above,  a block  of  pine  wood  must  be  prepared 
for  taking  the  impression.  This  piece  of  wood  should  be  long  enough 
to  get  the  impression  desired,  and  its  top  surface  should  be  cylindrical, 
with  a radius  \ inch  less  than  the  bore  of  the  gun.  Its  top  surface 
should  be  about  one-third  of  the  circumference  of  the  bore  or  less. 
A yf-inch  hole  should  be  bored  through  the  length  of  the  block.  The 
block  should  be  1 inch  thicker  at  one  end  than  the  other,  so  that  the 
lower  surface  will  act  as  a wedge.  (See  sketch  on  next  page.) 

In  the  top  surface  of  the  block  should  be  drilled  I-inch  holes  | inch 
deep,  spaced  about  2 inches  apart.  These  have  been  found  more  effi- 
cacious than  the  two  coats  of  shellac  formerly  prescribed  to  make  the 
gutta-percha  adhere  to  the  block.  Moreover,  the  time  required  for 
the  shellac  to  drv  is  saved. 


14 


Gutta-percha  on  which  the  impression  is  made.  (See  note.) 

A wedge  of  hardwood  is  also  required.  This  wedge  should  be  the 
same  length  as  the  block,  with  its  lower  surface  cylindrical,  and  of 
such  a size  that  when  the  block  and  wedge  are  placed  together,  their 
ends  flush,  the  combined  diameter  will  be  | inch  less  than  the  diam- 
eter of  the  bore.  A hole  is  bored  in  the  larger  end  of  the  wedge  to 
take  the  end  of  the  pole.  The  pole  is  driven  into  this  hole  and  secured 
in  place  by  a strong  wood  screw. 

Suppose  it  is  desired  to  take  the  impression  from  the  breech  of 
the  gun. 

The  iron  rod  is  placed  with  its  threaded  end  through  the  hole  in 
the  block  of  pine  wood  and  a nut  and  washer  at  each  end  oi  the 
block  are  used  to  secure  it  in  place.  The  unthreaded  end  of  the  rod 
should  project  from  the  small  end  of  the  block.  The  iron  bar  is  then 
fastened  to  the  rod,  so  that  the  distance  from  the  bar  to  the  middle 


of  the  block  of  wood  is  the  distance  from  the  breech  of  the  gun  to  the 
center  of  the  impression  desired. 

The  gun  should  be  well  cleaned  and  all  oil  carefully  removed. 

The  two  wedge  surfaces  on  the  block  of  pine  wood  and  the  hard- 
wood wedge  should  be  rubbed  with  tallow. 

Fill  the  kettle  partly  full  of  water  and  heat  it  to  about  190°  F. 
Place  the  gutta-percha  in  this  hot  water  and  let  it  remain  there  until 
soft.  When  soft  place  it  on  the  board,  which  has  been  first  wet  with 
water,  and  roll  the  rubber  out  until  it  is  of  proper  size.  Care  must 
be  taken  that  the  board  is  kept  wet,  and  that  the  gutta-percha  is  of 
an  even  thickness;  I inch  is  about  right.  The  sheet  of  gutta-percha 
is  then  placed  on  the  block  and  the  edges  trimmed  off  with  a pair 
of  shears.  The  top  surface  of  the  gutta-percha  is  then  rubbed  with 
graphite.  The  block  is  then  placed  in  the  gun,  the  bar  locating  it 
at  the  proper  distance,  and  the  wedge  is  driven  into  place.  When 
cool,  drive  out  the  wedge,  being  careful  that  the  impression  is  not 
moved  until  the  wedge  has  been  removed.  The  block  with  the 
impression  is  then  carefully  removed  and  trimmed. 


15 


The  sketch  below  shows  the  parts  assembled  and  in  the  gun. 


Note. — The  only  satisfactory  gutta-percha  obtained  for  the  pur- 
pose at  the  proving  ground  has  been  purchased  as  ‘‘gutta-percha 
for  taking  gun  impressions’^  from  the  Bishop  Gutta-Percha  Co., 
420  East  Twenty-fifth  Street,  New  York  City.  It  is  furnished  in 
slabs  about  20  inches  long,  5 inches  wide,  and  f inch  thick. 

War  Department, 

Office  of  the  Chief  of  Ordnance, 

Washington,  June  7,  1916. 

February  16,  1905. 

Revised  November  7,  1906. 

Revised  March  11,  1908. 

Revised  January  28, 1913. 

Revised  June  7, 1916. 

062.1-826  Revisions. 

Form  No.  1091. 

Ed.  June  7-16-500. 

O 


No. 


Preoaratorv  to  measurini?  chamber. 


